Synthesis and catalytic performance of nickel phosphinite pincer complexes in deoxygenative hydroboration of amides. Issue 9 (10th February 2023)

• Record Type: Journal Article
• Authors: Adilkhanova, Aziza; Frolova, Valeriya F.; Yessengazin, Azamat; Öztopçu, Özgür; Gudun, Kristina A.; Segizbayev, Medet; Matsokin, Nikita A.; Dmitrienko, Anton; Pilkington, Melanie; Khalimon, Andrey Y.
• Is Part Of: Dalton transactions. Volume 52:Issue 9(2023)
• Page Start: 2872
• Page End: 2886
• Publication Date: 2023-02-10
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d2dt03801c
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : A series of POCN R POCN R2 and POCOP pincer complexes of Ni(ii ) were prepared and their catalytic activities in deoxygenative hydroboration of amides were investigated, resulting in efficient and selective deoxygenation of secondary amides to amines. Abstract : A series of imino-POCN R, amino-POCN R2, and bis(phosphinite) POCOP pincer complexes of Ni(ii ) were prepared and tested in catalytic deoxygenative hydroboration of amides with HBPin to the corresponding amines. In contrast to the deoxygenative hydrosilylation approach, primarily developed for tertiary amides, superior reactivity in Ni-catalyzed deoxygenative hydroboration was demonstrated for secondary carboxamides. The bis(phosphinite) hydride complex (POCOP)NiH proved the most active in these reactions, tolerating potentially reducible functionalities such as internal alkenes, esters, nitriles, heteroaromatic compounds, and tertiary amides. Preferable hydroboration of secondary amides was also demonstrated in the presence of primary amide functionalities. The reactions were conducted at 60–80 °C, representing a rare example of a base-metal catalytic system for selective deoxygenation of secondary amides to the corresponding amines under mild conditions. In contrast to secondary amides, deoxygenative hydroboration of primary amides was demonstrated using an iminophosphinite pre-catalyst (POCN Dmp )Ni(CH2 TMS) (Dmp = 2, 6-Me2 C6 H3 ). Deoxygenation reactions were suggested to proceed via a direct C–O bond cleavage mechanism, which is triggered by dehydrogenative N -borylation to access more electrophilic N -borylamides amenable to the addition of HBPin to the carbonyl group.